Sensor Degradation
It’s a snowy night, and you’re about to use the ATM outside your local grocery store that’s been there for years. You enter in your access code, and notice only 2 of the 4 entries are reflected on the display.
You clear the entry, and strike each number on the monitor again. Again the entry seems off.
Now your card is eaten up in that darned machine.
The touch screen doesn’t work.
What is really happening is that the touch screen isn’t working as well as it used to. Several factors can lead to sensor degradation. This sensor degradation, when not accounted for, can push the operating specifications of your touch controller and sensor pair out of functioning range.
Resistive touch panels are made of two sheets of conductive material. This conductive material needs to be uniformly coated on both sides. When you press a resistive panel, one side smushes into the other side. The bending of the flexible layer, referred to as the “flex” layer which is often made of polyester, into the glass or plastic layer, the “stable” layer, is what makes the resistive touch solution work and move your cursor. The conductive coating afixed to the flex layer is bent and stretched when the polyester layer comes in contact with a user’s finger or stylus. The metallic conductive coating does not have the same flexible properties as this polyester layer, and can stretch and crack with repeated use.
The humidity and the temperature of the environment also affects the wear and tear seen by the resistive panel. The air trapped inside the resistive panel is maintained by adding a layer, often called spacer dots, between the flex and the stable. Typically, this is maintained when the environment remains static. When the temperature rises or falls dramatically, the air within the sensor will expand or contract, stretching the polyester layer again. Thusly, the uniform coating becomes less uniform, and the sensor’s electrical properties are again compromised. The resistance of the panel will increase as the coating cracks, and the capacitance between the two conductive layers will increase as the polyester relaxes.”
While there are coatings and heaters and special manufacturing precautions to add to the longevity of the sensor, the sensor will eventually succumb to wear and tear and stop functioning. It’s up to the touch controller to be designed with a wide window of operation so that it will continue to function for as long as possible.